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| Titel |
Assessment of heat sources on the control of fast flow of Vestfonna ice cap, Svalbard |
| VerfasserIn |
M. Schäfer, F. Gillet-Chaulet, R. Gladstone, R. Pettersson, V. A. Pohjola, T. Strozzi, T. Zwinger |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 8, no. 5 ; Nr. 8, no. 5 (2014-10-27), S.1951-1973 |
| Datensatznummer |
250116330
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| Publikation (Nr.) |
 copernicus.org/tc-8-1951-2014.pdf |
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| Zusammenfassung |
Understanding the response of fast flowing ice streams or outlet glaciers to
changing climate is crucial in order to make reliable projections of sea
level change over the coming decades. Motion of fast outlet glaciers occurs
largely through basal motion governed by physical processes at the glacier
bed, which are not yet fully understood. Various subglacial mechanisms have
been suggested for fast flow but common to most of the suggested processes is
the requirement of presence of liquid water, and thus temperate conditions.
We use a combination of modelling, field, and remote observations in order to
study links between different heat sources, the thermal regime and basal
sliding in fast flowing areas on Vestfonna ice cap. A special emphasis lies
on Franklinbreen, a fast flowing outlet glacier which has been observed to
accelerate recently. We use the ice flow model Elmer/Ice including a Weertman
type sliding law and a Robin inverse method to infer basal friction
parameters from observed surface velocities. Firn heating, i.e. latent heat
release through percolation of melt water, is included in our model; its
parameterisation is calibrated with the temperature record of a deep borehole.
We found that strain heating is negligible, whereas friction heating is
identified as one possible trigger for the onset of fast flow. Firn heating
is a significant heat source in the central thick and slow flowing area of
the ice cap and the essential driver behind the ongoing fast flow in all
outlets.
Our findings suggest a possible scenario of the onset and maintenance of fast
flow on the Vestfonna ice cap based on thermal processes and emphasise the
role of latent heat released through refreezing of percolating melt water for
fast flow. However, these processes cannot yet be captured in a temporally
evolving sliding law. In order to simulate correctly fast flowing outlet
glaciers, ice flow models not only need to account fully for all heat
sources, but also need to incorporate a sliding law that is not solely based
on the basal temperature, but also on hydrology and/or sediment physics. |
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